Expansion joints are generally provided in the structure after every 50 m.
Generally, premould bituminous sheets are used as a back-up material and two component polysulphide sealant (base and accelerator) is used for sealing exterior part of the joint with special primer as a bonding agent.
Surface preparation for expansion joint waterproofing.
Clean the joint surface of dust, cement mortar etc.
Remove oil grease (if any), from the surface.
Protect the edges of the joint with a masking tape, from the over filled sealant material.
Keep the tools like suspended scaffolding (zula), ladder, spatula, putty knife, hand held gun equipment etc. ready.
Work procedure for vertical expansion joint waterproofing
Primer is applied in the joint, in accordance with the type of the joint, e.g. for surfaces like concrete, masonry etc.
After the primer dries completely, sealant is prepared by mixing base and accelerator. Mixing should continue until colour is obtained.
The base and accelerator is mixed together in proportion by weight.
This mixed compound is then applied with a spatula of hand held gun equipment wherever required. Extra material is cut off with putty knife and a smooth vertical joint is created.
Since the sealant is very expensive, use it economically. The outermost surface of the sealant should present a slightly concave surface in profile.
Remove the masking tape and clean the surface with suitable solvents.
